Treatment of hides, skins, and leather



Patented May is, 1939 um'rrzo STATES TREATMENT OF RIDES, SKINS, AND LEATHER Wolf Krltchevsky, Chicago, m., asslgnor to Nlnol, Inc., Chicago, 111., a corporation of Illinois No Drawing. Application March 25, 1938, Serial No. 198,029

22 Claims. (01. 149-5) My invention relates to the treatment of hide substance, including untanned, partially tanned as well as fully tanned leathers.

In accordance with prior art practice, before hide substance is converted into leather a preliminary series of operations are carried out such as soaking, liming, bating, and the like.

In general, there are two tanning procedures employed on a large scale, namely, vegetable tanning and chrome tanning or tanning with similar inorganic reagents. The employment of either vegetable tanning or chrome tanning or the like is governed by various considerations, chief among which is the nature of the uses to which the final leather is to be put. In recent years, synthetic tanning agents have been employed to some extent but they are used chiefly in conjunction with the tanning procedures previously described. The tanning operation serves to convert the hide substance into a product which is free from putrefactive tendencies, is relatively soft and pliable, and withstands the effect of water; in other words, it converts the hide sub-.

stance into the product which we know as leather. Among the disadvantages of the tanning process, as practiced today, is the fact that a considerable period of time is consumed in carrying out the same. In the case of vegetable tanning, the operation usually takes at least a few months and in certain instances'much longer. The chrome tanning operation, although effected more rapidly than the vegetable tanning, still requires at least several hours in the usual case.

I have made the startling discovery that untanned hide substance, that is, the hide substance in the form in which it appears after the so-called beam house operations, and also the hide substance of fur skins, can be converted into a substance having many of the characteristics of leather by a simple operation which can be carried" out in a relatively fewminutes. The products produced in accordance with my invention are characterized by the appearance, feel and freedom from putrefactive properties which are associated with ordinary leather. They are soft, pliable and possess unexpected tensile strength, in many cases being considerably stronger in this regard than ordinary leather.

I have also discovered that my invention be practiced with very eflicacious results not only with respect to untanned hide substance but also in connection with the treatment of partially tanned or completely tanned hides. In these latter cases, the practice of my invention, in general, imparts to the treated hide substance 9.

flufliness, softness, silkiness, pllability and increased tensile strength.

In general, my invention is predicated on the discovery that certain compounds, hereinafter described, may be caused to impregnate untanned 5 hide substance or partially or completely tanned hide substance whereby the properties noted above are imparted to said hide substance. The compounds which I have found effective for this purpose are, in general, ethers of aliphatic polyhydric alcohols, said compounds containing at least six carbon atoms and preferably at least eight carbon atoms. Some of the ether derivatives which I have found particularly useful may be represented by the general formula:

wherein R and R are selected from the group consisting of hydrogen, alkyl, cycloalkyl, and

substitution products thereof, R and R, are al- 20 kylene or hydroxy, halogen, alkyl or otherwise substituted alkylene, a: is zero or one, and n is a small whole number, at least one of R and R being other than hydrogen when a: is zero, said compounds containing at least six carbon atoms 25 and preferably at least eight. The aliphatic polyhydric alcohols from which the ethers which I employ herein may be derived include the glycols such as ethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, tripro- 30 pylene glycol, propylene glycol, butylene glycol, amylene glycol, and the like; polyglycols such as diethylene glycol, dipropylene glycol, dibutylene glycol, diamylene glycol and the higher polyglycols; glycerol; polyglycerols such as diglycerol, 35 triglycerol, tetraglycerol and the like; sugars and sugar alcohols including, for example, sucrose, dextrose, maltose, levulose, rhamnose, sorbitol, mannitol dulcitol; pentaerythritol andthe like. I have found that the 'ether derivatives of glycols 40 and particularly of polyglycols are unusually satisfactory. There may be one or more ether linkages in the compounds which I employ herein but in all'cases there is at least one such linkage. The agents may contain one or more free hy- 45 droxyl groups or there may beno free hydroxyl groups. In some cases, I have obtained particularly satisfactory results where the agent which I employed was devoid of free hydroxyyl groups.

Among the specific compounds which may be 50 employed with effective results are the following, these being recited simply as representative of the large class which appear to be highly useful for my present purposes. It will be understood, of course, that mixtures of any two or more of said agents may be employed and that the same may be utilized in impure or commercial form:

Ethylene glycol monobutyl ether, diethylene glycol mono-ethyl ether, dipropylene glycol, dibutylene glycol, mono-hexyl ether of ethylene glycol, tetrapropyleneglycol, mono-cyclohexyl ether of diethylene glycol, mono-cyclohexyl ether of dipropylene or tri-propylene glycol, dipropylene glycol, tri-propylene glycol, tri-butylene glycol, methyl amyl ether of tetraethylene glycol, monolauryl ether of diethylene glycol, mono-cetyl ether of diethylene glycol, mono-octyl ether of trimethylene glycol, mono-lauryl ether of propylene glycol, mono-stearyl ether of propylene glycol, mono-butyl ether of diethylene glycol, monobutyl ether of triethylene glycol, mono-butyl ether of tetraethylene glycol, di-cyclohexyl ether of diethylene glycol, di-butyl ether of triethylene glycol, mono-octyl ether of glycerol, di-cyclohexyl ethers of glycerol, diethyl ether of diethylene glycol, mono-amyl ether of diethylene glycol, monobutyl ether of triethylene glycol, 2-ethyl butyl ether of diethylene glycol (mono-ether), monooctyl ether of mannitol, mono-lauryl ether of sorbitol, di-hexyl ether of mannitol, and the like. The mechanics of the process of carrying out my invention involve simply effecting an adequate contact between the hide substance and the.

treating agent in a manner such as to cause the absorption by the hide substance of preferably at least several percent of the treating agent. This may be accomplished, for example, by immersion oi the hide substance in a bath of the treating agent or by brushing or spraying the latter on the hide substance or otherwise mechanically working the same thereinto in sufficient amount so as to cause the desired degree of absorption. In general, in most cases the amount of agent employed should be such that the hide substance absorbs not substantially less than 4% of the treating agent, based upon the weight of the untreated hide substance. Usually, the hide substance will have the capacity to absorb substantially greater amounts of said agents, in many instances, as high as 25% and even greater. I have found, however, that, at least in most instances, the absorption of more than 12% to 15% of said treating agent based on the weight of the wet or untreated hide, does not produce materially better results than accrue from the absorption of say 4% to 10%. Accordingly, in the light of economic considerations, the absorption of between about 4% and 10% will serve the purpose adequately in the case of most of the compounds which I may employ herein.

The effect of the impregnation of, for example, the untanned hide substance by the agents described hereinabove in accordance with my invention is akin to that of tanning. That is, the untanned hide substance is converted into a product which has the appearance, softness and pliabillty and general feel of leather, and is free from the tendency to putrefy. The process is, generally speaking, not strictly a tanning process in that, with certain of the treating agents, by prolonged washing of the final product with water, the leather-like properties brought about by the impregnation with said certain agents are to some extent lost. It is for this reason that I prefer to characterize the products resulting from the treatment in accordance with my invention as leatherlike rather than leather. It will be understood, however, that the resistance of the product to water varies with the particular agent with which it is impregnated and, in certain instances,

. in the claims. tions may be made in the length of contact of the particularly with the higher molecular weight ether derivatives, namely, those containing at least eight carbon atoms, the tendency for reconversion to hide substance by washing with water is substantially inhibited.

I have adverted hereinabove to the fact that my process may be employed with considerable efficiency in the treatment of partially tannedfor completely tanned hide substances. In this connection, I may state that the utilization of a partial pre-tanning of hide or skin, followed by the impregnationof the resulting pre-treated or pre-tanned hide or skin, with the agents which I have described hereinabove represents a particularly satisfactory embodiment of my invention. In this case, the final product has an excellent feel and appearance and a substantially increased tensile strength. By virtue of the pre-tanning to which the hide or skin is subjected, it has the characteristics of true leather and the treatment with the ether derivatives which I have disclosed hereinabove imparts the desirable properties of fluiiiness, fullness, and increased tensile strength to the finished product.

Among the advantages which the practice of my invention brings about are, first, a marked reduction in the length of time required to convert untanned hide substance or partially tanned hide substance into a product having leatherlike characteristics. As against at least several months or at least several hours for carrying out conventional tanning, depending upon the particular process employed, the practice of my invention can be effected in a relatively few minutes, apparently independently of the thickness of the raw or untreated hide substance. Furthermore, the practice of my invention eliminates the necessity for the conventional fat-liquoring treatment to which leather is subjected. Indeed, the practice of my invention may be said to bring about the effects of fat-liquoring and tanning in a simultaneous operation. Another important advantage of the practice of my invention resides in the fact that it serves to replace or supplement chrome and vegetable tanning processes and, particularly, corrects some of the defects of chrome leather such as high acidity and high conductivity of heat and cold.

An usual aspect of the practice of my invention is the fact that the impregnation of hide substance with at least many of the ether derivatives which I have disclosed hereinabove causes the hide substance to become practically pure white in color, this efiect being in addition to the conversion of the hide substance into a product having a leathery appearance, soft feel, and extraordinary tensile strength. Just what the mechanism of the process is which brings about this remarkable change in color has not yet been fully ascertained and I prefer not to theorize with respect thereto.

In order that those skilled in the art may even more fully understand the full scope of my invention, I shall describe a few illustrative examples for carrying out my invention. It will be understood, however, that the same are not to be construed in any way as limitative of the true scope of my invention, the latter being pointed out It will be understood that variahide substance with the agent, the concentration of the agent and the selection of the particular agent to be employed. Those skilled in the art will, in the light of my teachings herein, be able to make various adjustments all of which,

however, will'fall within the scope of my novel teachings.

. Example 1 Example If A piece of untanned hide of cows was swabbed or rubbed with sufllcient diethyl ether of diethylene glycol so that the hide substanceabsorbed approximately 5% said ether. The final product was leather-like in appearance, was snow white in color and had excellent tensile strength.

A similar sample was made with 10% of absorbed diethyl ether of diethylene glycol and had generally similar properties to the product which contained only 5% thereof. Aside from haying slightly better resistance to washing with water, it did not appear to offer .any marked advantage over the product containing only 5%.

Example III Untanned hide substance was impregnated with an amount of the mono cyclohexyl ether of diethylene glycol equal to approximately 10% by white in'color, soft in feel, and had satisfactory resistance to washing with water.

with respect to those of my treating agents which are water-insoluble or have little aflinity for water, it is usually necessary to employ a penetrating or dispersing agent or the like tocause said treating agents to penetrate adequately into or through the hidesubstance. In this connection, it should be understood that the hide substance, prior to treatment with the agents herein described, contains a substantial percentage of water, in manycases in the neighborhood of 70% by weight of the hide substance. Hence, in order to get adequate penetration thereinto of treating agents which have little afllnity for water,- a dispersing or penetrating agent or mutual solvent for water and the treating agent may be employed with advantage. Such penetrating agents and mutual solvents include, for

weight of the raw material. The resulting prodnot was white, had the appearance, feel and pliability of leather together with substantially increased tensile strength.

Example IV Untanned hide substance was impregnated with the 2-.ethyl butyl' ether of diethylene glycol (mono-ether) to incorporate approximately 10% of said ether, based upon the weight of the raw material.- In another-case, the'amount of said ether absorbed was 15%, based on the weight of the raw material. In each instance the resulting product was leather-like in general appearance and characteristics, was practically snow white in color and had unusually high tensile strength.

Example V (a) 'Uhtanned hide was pre-tanned with a chromium sulphate solution for V hour, was

sirable characteristics described hereinabove.

Example VI (a) Untanned hide was pre-tanned with a 2% solution of formaldehyde in water, the hide being kept in contact with the formaldehyde solution for 12 hours. The hide, which had turned white,

was then rubbed with the monobutyl ether of diethylene glycol until it absorbed about 8% of its weight thereof. The resulting article .was

example, methyl-alcohol, ethyl alcohol, propyl alcohol, acetone and the like. In certain cases, eflective results are obtained by using, in combination with the treating agent, another treating agent which in itself'has penetrating or mutual solvent properties. Examples of such agents are monobutyl ether of ethylene glycol, monoethyl ether of diethylene glycol, monobutyl ether of diethylene glycol, and the like. Other agents which may be employed to effect penetration of the treating agent into the fibers of the hide substance are various of the organic wetting agents. Impregnation may also be effected by mechanical means such as the use of alternate vacuum and pressure on the hide substance while disposed in a bath of the treating agent in a closed vessel. In general, it is preferred to utilize treating agents which possess some aflinity for water but insuflicient to cause the same to be washed out from the treated hide substance too readily with water.

As has been stated hereinabove. the practice of my process results in the elimination of the usual fat-liqu0ring step. In this connection, it should be noted that in conventional chrome tanning operations itis necessary to insure that the leather, prior to the fat-liquoring operation, is substantially neutral since excess acidity or alkalinity in the leather will break down the constituents of the fat liquor. When my invention is practiced, in conjunction with a pre-treating by chrome or the like, it is unnecessary to go through the steps of neutralizing the excess acidity in the leather prior to the treatment with the ether derivatives ofmy invention because said derivatives appear to be unaffected by whatever the condition of the leather may be.

It should be understood that, where the subjection of the hide or the like to treatment with the ether derivatives of my invention is preceded by a tanning operation, said tanning operation may be carried out in accordance with known methods such as by the use of vegetable tanning agents such as hemlock or quebracho; chrome, alum, iron or other mineral or inorganic tanning agents; or synthetic agents including, for example, aldehydes such as formaldehyde, quinone and quinones, naphthol compounds, condensation products of phenols and polyphenols, monoand poly-nuclear, with aldehydes such as formaldehydes; or combinations of said tanning agents or tanning procedures. In so far as the pH of such tannages is concerned, it will be understood that the range thereof may accord with known practices. While, as indicated, for example, in

Example VI, the treatment with the compounds of myinvention is preceded by a tannage, it is by no means necessary that such order of steps be employed. The treatment may take place with the different agents simultaneously and, in various eases, the treatment with the compounds of my invention may precede treatment with the synthetic tanning agents and the like. when formaldehyde or like tanning agents are employed in my invention, particularly in the presence of small amounts of alkali, it appears that some sort of reaction takes place between the 'formaldelwde and the compounds of my 'invenalso be prepared while still enjoying the advantages of my novel teachings. In this connection, the dyeing or coloring of the hide substance or leather-like product should be carried ,out

. preferably either before the step of impregnating with the ether derivatives or simultaneously therewith.

While I have described the impregnation of hide substances with ether derivatives as such, it should not be inferred that said ether derivatives need be employed in pure form. For example, the ether derivatives may be dissolved in suitable solvents such as organic solvents, as, for example, alcohol and, in certain cases, water. In case water is used as a solvent, however, care should be taken that it is not used in suihcient quantities to counteract the effect of the ether derivatives, this being particularly the case with respect to those ether derivatives which are not so strongly resistant to being washed out from the hide substance with water. Although, for example, satisfactory results can be obtained by using aqueous solutions of monobutyl ether of diethylene glycol containing as low as about 20% of said ether, it is preferred to utilize either the ether derivatives as such or relatively strong solutions thereof. It will be understood, in brief, that the invention covers the impregnation of hide substance with said ether derivatives in any manner in which it is found desirable to effect such impregnation and in amount suflicient to obtain the results indicated hereinabove.

It is to be understood that the leather or leather-like products of my invention may and usually will be subjected to the regular mechanical or rubbing and like operations to which ordinarily tanned leather is subjected, for example, to render the product softer and more flexible.

It will be understood that the term "hide sub-- stance" includes pelts and skins from cows, oxen, horses, calves, goats, sheep, dogs, buffalo, walrus or other animals whose skins are usually converted into leather by a tanning process. Furthermore, while my invention has particular applicability to the conversion of hide substances of the type indicated into leather-like materials, it also hasmarked value, as previously indicated, in connection with the tanning of the skin or hide substance of animal furs such as sheep skin, fox, beaver, rabbit, skunk, squirrel, seal, raccoon, and the like. In this case, the practice of my invention renders the leather portion of the furs soft and pliable and enhances the strength thereof whereby the usual sewing operations thereon may amass? be conducted with less danger of damage to the fur. Furthermore, the hair portion of the skin is in no wise adversely affected. Hence, wherever, the term hide substance" is employed herein and in the claims, it will be understood to cover all such materials as indicated.

'While the treating agents which I have described hereinabove possess a tanning action and are employed primarily for that purpose, I have also found that they may be utilized in place of .the conventional fat-liquoring and as constitu cuts of the otherwise ordinary fat liquors. In other words, they may be employed for the treatment of previously tanned leather to impart softness, flexibility, suppleness and like properties to tanned leather.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. The method of treating a material selected from the group consisting of untanned and at least partially tannedhide substance which comprises contacting it with a compound in the form of an ether of an aliphatic polyhydric alcohol, said compound containing at least six carbon atoms, whereby said hide substance is caused to absorb at least several percent of said compound.

2. The method of claim 1, wherein the alcohol is a dihydric alcohol.

'3. The method of claim 1, wherein the alcohol is a polyglycol, and the amount of the compound absorbed is not substantially less than 4%.

4. The method of treating a material selected from the group consisting of. untanned and at least partially tanned hide substance which comprises contacting it with acompound in the form of an aliphatic polyhydric alcohol wherein the hydrogen 0! at least one alcoholic hydroxy group thereof is replaced by a radical selected from the group consisting of alkyls, cycloalkyls, and substitution products thereof, said compound containing at least six carbon atoms, whereby said hide substance is caused to absorb at least several percent of said compound.

5. The method of'claim 1, wherein the alcohol is a glycol and wherein the compound contains at least eight carbon atoms.

6. The method of treating a material selected from thegroupconsisting of untanned and at least partially tanned hide substance which comprises contacting with a compound having the general formula wherein R and R are selected from the group 2 character which comprises impregnating said untanned hide substance with a compound in the form of an ether of an aliphatic polyhydric alcohol, said compound containing at least six 'carbon atoms, whereby the hide substance is caused to absorb not substantially less than 4% of said compound.

9. The method of converting untanned or partially tanned hide substance into a product having a leather-like character which comprises impregnating the same with an ether of a polyglycol, containing at least six'carbon atoms, whereby the hide substance is caused to absorb between about 4% and 15% of said ether.

10. The method of claim 8 wherein the compound is characterized by the absence of free hydroxyl groups.

11. The method of claim 8 wherein the compound is characterized by the presence of only one free hydroxyl group.

12. Untanned or at least partially tanned hide substance impregnated with at least several percent of a chemical compound in the form of an ether of an aliphatic polyhydric alcohol, said compound containing at least six carbon atoms.

13. The product of claim 12, wherein the alcohol is a dihydric alcohol.

14. The product of claim 12, wherein the alcohol is a polyglycol, and the amount of the compound absorbed is not substantially less than 4%.

15. Untanned or at least partially tanned hide substance impregnated with at least several percent of a chemical compound in the form of an aliphatic polyhydric alcohol whereinthe hydrogen of at least one alcoholic hydroxy group thereof is replaced by a radical selected from the group consisting of alkyls, and cycloallgyls, and substitution products thereof, said compound containing at least six carbon atoms.

16. The product of claim 15 wherein the alcohol is a glycol and wherein the compound contains at least eight carbon atoms.

17. Untanned or at least partially tanned hide substance impregnated with at least several percent of a chemical compound having the general formula wherein R and R are selected from the group consisting of hydrogen, 'alkyl, cycloalkvl, and substitution products thereof, R and R. are alkylene or substituted alkylene, x is zero or one, and n is a small whole number, at least one of R and R being other than hydrogen when a: is zero, said compound containing at least six carbon atoms.

18. The product of claim 17 wherein the compound is an ether derivative of diethylene glycol.

19. Untanned hide substance having the appearance, feel and freedom from putrefaction properties which characterize leather, said properties accruing by reason of the impregnation of the untanned hide substance with a compound in the form of an ether of an aliphatic polyhydric alcohol, which compound contains at least six carbon atoms.

20. The product of claim 19, wherein the compound is an ether of a polyglycol and the amount thereof which is absorbed by the hide substance is between about 4% and 21. Untanned hide substance, white in color, and characterized by the appearance, feel and freedom from putrefaction properties of leather, said properties accruing by reason of the impregnation of the untanned hide substance with a compound corresponding to the formula.

RO-(R [0]z-R )n-OR wherein R, and R are selected from the group consisting of hydrogen, alkyl, cycloalkyl, and substitution products thereof, R and R are alkylene or substituted alkylene, a: is zero or one, and n is a whole number, at least one of R and R being other than hydrogen when a: is zero.

22. The product of claim 21, wherein R and R are each CzHs, a: is one, and n is one.

WOLF KRI'ICHEVSKY. 

